Table 4

Quality analysis of included studies

SelectionComparabilityOutcomeTotal score
(1–9)
(1)
Representativeness of the exposed cohort
(2)
Selection of the non-exposed cohort
(3)
Ascertainment of exposure
(4)
Demonstration that outcome of interest was not present at start of study
(1)
Study controls for age, height, BMI, BP and gender (select the most important factor)
(2)
Study controls for any additional factor
(1)
Assessment of outcome
(2)
Was follow-up long enough for outcomes to occur
(3)
Adequacy of follow-up of cohorts
Kallio et al281110111118
Geerts et al271110111118
Yang et al291010001003
Ayer et al241110111118
  • Note 1: 8–9 points stand for very good study quality; 6–7 points stand for good study quality; 4–5 points stand for satisfactory study quality; 0–3 points stand for unsatisfactory study quality.

  • Note 2: The Newcastle-Ottawa scale (online supplemental file A).

  • BMI, body mass index; BP, blood pressure.